# Django 2.0.dev20170216164632 documentation

# Source code for django.urls.resolvers

    """
    This module converts requested URLs to callback view functions.

    RegexURLResolver is the main class here. Its resolve() method takes a URL (as
    a string) and returns a ResolverMatch object which provides access to all
    attributes of the resolved URL match.
    """
    import functools
    import re
    import threading
    from importlib import import_module
    from urllib.parse import quote

    from django.conf import settings
    from django.core.checks import Warning
    from django.core.checks.urls import check_resolver
    from django.core.exceptions import ImproperlyConfigured
    from django.utils.datastructures import MultiValueDict
    from django.utils.encoding import force_text
    from django.utils.functional import cached_property
    from django.utils.http import RFC3986_SUBDELIMS
    from django.utils.regex_helper import normalize
    from django.utils.translation import get_language

    from .exceptions import NoReverseMatch, Resolver404
    from .utils import get_callable

    class ResolverMatch:
        def __init__(self, func, args, kwargs, url_name=None, app_names=None, namespaces=None):
            self.func = func
            self.args = args
            self.kwargs = kwargs
            self.url_name = url_name

            # If a URLRegexResolver doesn't have a namespace or app_name, it passes
            # in an empty value.
            self.app_names = [x for x in app_names if x] if app_names else []
            self.app_name = ':'.join(self.app_names)
            self.namespaces = [x for x in namespaces if x] if namespaces else []
            self.namespace = ':'.join(self.namespaces)

            if not hasattr(func, '__name__'):
                # A class-based view
                self._func_path = '.'.join([func.__class__.__module__, func.__class__.__name__])
            else:
                # A function-based view
                self._func_path = '.'.join([func.__module__, func.__name__])

            view_path = url_name or self._func_path
            self.view_name = ':'.join(self.namespaces + [view_path])

        def __getitem__(self, index):
            return (self.func, self.args, self.kwargs)[index]

        def __repr__(self):
            return "ResolverMatch(func=%s, args=%s, kwargs=%s, url_name=%s, app_names=%s, namespaces=%s)" % (
                self._func_path, self.args, self.kwargs, self.url_name,
                self.app_names, self.namespaces,
            )

    @functools.lru_cache(maxsize=None)
    def get_resolver(urlconf=None):
        if urlconf is None:
            from django.conf import settings
            urlconf = settings.ROOT_URLCONF
        return RegexURLResolver(r'^/', urlconf)

    @functools.lru_cache(maxsize=None)
    def get_ns_resolver(ns_pattern, resolver):
        # Build a namespaced resolver for the given parent URLconf pattern.
        # This makes it possible to have captured parameters in the parent
        # URLconf pattern.
        ns_resolver = RegexURLResolver(ns_pattern, resolver.url_patterns)
        return RegexURLResolver(r'^/', [ns_resolver])

    class LocaleRegexDescriptor:
        def __get__(self, instance, cls=None):
            """
            Return a compiled regular expression based on the active language.
            """
            if instance is None:
                return self
            # As a performance optimization, if the given regex string is a regular
            # string (not a lazily-translated string proxy), compile it once and
            # avoid per-language compilation.
            if isinstance(instance._regex, str):
                instance.__dict__['regex'] = self._compile(instance._regex)
                return instance.__dict__['regex']
            language_code = get_language()
            if language_code not in instance._regex_dict:
                instance._regex_dict[language_code] = self._compile(force_text(instance._regex))
            return instance._regex_dict[language_code]

        def _compile(self, regex):
            """
            Compile and return the given regular expression.
            """
            try:
                return re.compile(regex)
            except re.error as e:
                raise ImproperlyConfigured(
                    '"%s" is not a valid regular expression: %s' % (regex, e)
                )

    class LocaleRegexProvider:
        """
        A mixin to provide a default regex property which can vary by active
        language.
        """
        def __init__(self, regex):
            # regex is either a string representing a regular expression, or a
            # translatable string (using gettext_lazy) representing a regular
            # expression.
            self._regex = regex
            self._regex_dict = {}

        regex = LocaleRegexDescriptor()

        def describe(self):
            """
            Format the URL pattern for display in warning messages.
            """
            description = "'{}'".format(self.regex.pattern)
            if getattr(self, 'name', False):
                description += " [name='{}']".format(self.name)
            return description

        def _check_pattern_startswith_slash(self):
            """
            Check that the pattern does not begin with a forward slash.
            """
            regex_pattern = self.regex.pattern
            if not settings.APPEND_SLASH:
                # Skip check as it can be useful to start a URL pattern with a slash
                # when APPEND_SLASH=False.
                return []
            if (regex_pattern.startswith('/') or regex_pattern.startswith('^/')) and not regex_pattern.endswith('/'):
                warning = Warning(
                    "Your URL pattern {} has a regex beginning with a '/'. Remove this "
                    "slash as it is unnecessary. If this pattern is targeted in an "
                    "include(), ensure the include() pattern has a trailing '/'.".format(
                        self.describe()
                    ),
                    id="urls.W002",
                )
                return [warning]
            else:
                return []

    class RegexURLPattern(LocaleRegexProvider):
        def __init__(self, regex, callback, default_args=None, name=None):
            LocaleRegexProvider.__init__(self, regex)
            self.callback = callback  # the view
            self.default_args = default_args or {}
            self.name = name

        def __repr__(self):
            return '<%s %s %s>' % (self.__class__.__name__, self.name, self.regex.pattern)

        def check(self):
            warnings = self._check_pattern_name()
            if not warnings:
                warnings = self._check_pattern_startswith_slash()
            return warnings

        def _check_pattern_name(self):
            """
            Check that the pattern name does not contain a colon.
            """
            if self.name is not None and ":" in self.name:
                warning = Warning(
                    "Your URL pattern {} has a name including a ':'. Remove the colon, to "
                    "avoid ambiguous namespace references.".format(self.describe()),
                    id="urls.W003",
                )
                return [warning]
            else:
                return []

        def resolve(self, path):
            match = self.regex.search(path)
            if match:
                # If there are any named groups, use those as kwargs, ignoring
                # non-named groups. Otherwise, pass all non-named arguments as
                # positional arguments.
                kwargs = match.groupdict()
                args = () if kwargs else match.groups()
                # In both cases, pass any extra_kwargs as **kwargs.
                kwargs.update(self.default_args)
                return ResolverMatch(self.callback, args, kwargs, self.name)

        @cached_property
        def lookup_str(self):
            """
            A string that identifies the view (e.g. 'path.to.view_function' or
            'path.to.ClassBasedView').
            """
            callback = self.callback
            # Python 3.5 collapses nested partials, so can change "while" to "if"
            # when it's the minimum supported version.
            while isinstance(callback, functools.partial):
                callback = callback.func
            if not hasattr(callback, '__name__'):
                return callback.__module__ + "." + callback.__class__.__name__
            return callback.__module__ + "." + callback.__qualname__

    class RegexURLResolver(LocaleRegexProvider):
        def __init__(self, regex, urlconf_name, default_kwargs=None, app_name=None, namespace=None):
            LocaleRegexProvider.__init__(self, regex)
            # urlconf_name is the dotted Python path to the module defining
            # urlpatterns. It may also be an object with an urlpatterns attribute
            # or urlpatterns itself.
            self.urlconf_name = urlconf_name
            self.callback = None
            self.default_kwargs = default_kwargs or {}
            self.namespace = namespace
            self.app_name = app_name
            self._reverse_dict = {}
            self._namespace_dict = {}
            self._app_dict = {}
            # set of dotted paths to all functions and classes that are used in
            # urlpatterns
            self._callback_strs = set()
            self._populated = False
            self._local = threading.local()

        def __repr__(self):
            if isinstance(self.urlconf_name, list) and len(self.urlconf_name):
                # Don't bother to output the whole list, it can be huge
                urlconf_repr = '<%s list>' % self.urlconf_name[0].__class__.__name__
            else:
                urlconf_repr = repr(self.urlconf_name)
            return '<%s %s (%s:%s) %s>' % (
                self.__class__.__name__, urlconf_repr, self.app_name,
                self.namespace, self.regex.pattern,
            )

        def check(self):
            warnings = self._check_include_trailing_dollar()
            for pattern in self.url_patterns:
                warnings.extend(check_resolver(pattern))
            if not warnings:
                warnings = self._check_pattern_startswith_slash()
            return warnings

        def _check_include_trailing_dollar(self):
            """
            Check that include is not used with a regex ending with a dollar.
            """
            regex_pattern = self.regex.pattern
            if regex_pattern.endswith('$') and not regex_pattern.endswith(r'\$'):
                warning = Warning(
                    "Your URL pattern {} uses include with a regex ending with a '$'. "
                    "Remove the dollar from the regex to avoid problems including "
                    "URLs.".format(self.describe()),
                    id="urls.W001",
                )
                return [warning]
            else:
                return []

        def _populate(self):
            # Short-circuit if called recursively in this thread to prevent
            # infinite recursion. Concurrent threads may call this at the same
            # time and will need to continue, so set 'populating' on a
            # thread-local variable.
            if getattr(self._local, 'populating', False):
                return
            self._local.populating = True
            lookups = MultiValueDict()
            namespaces = {}
            apps = {}
            language_code = get_language()
            for pattern in reversed(self.url_patterns):
                if isinstance(pattern, RegexURLPattern):
                    self._callback_strs.add(pattern.lookup_str)
                p_pattern = pattern.regex.pattern
                if p_pattern.startswith('^'):
                    p_pattern = p_pattern[1:]
                if isinstance(pattern, RegexURLResolver):
                    if pattern.namespace:
                        namespaces[pattern.namespace] = (p_pattern, pattern)
                        if pattern.app_name:
                            apps.setdefault(pattern.app_name, []).append(pattern.namespace)
                    else:
                        parent_pat = pattern.regex.pattern
                        for name in pattern.reverse_dict:
                            for matches, pat, defaults in pattern.reverse_dict.getlist(name):
                                new_matches = normalize(parent_pat + pat)
                                lookups.appendlist(
                                    name,
                                    (
                                        new_matches,
                                        p_pattern + pat,
                                        dict(defaults, **pattern.default_kwargs),
                                    )
                                )
                        for namespace, (prefix, sub_pattern) in pattern.namespace_dict.items():
                            namespaces[namespace] = (p_pattern + prefix, sub_pattern)
                        for app_name, namespace_list in pattern.app_dict.items():
                            apps.setdefault(app_name, []).extend(namespace_list)
                    if not getattr(pattern._local, 'populating', False):
                        pattern._populate()
                    self._callback_strs.update(pattern._callback_strs)
                else:
                    bits = normalize(p_pattern)
                    lookups.appendlist(pattern.callback, (bits, p_pattern, pattern.default_args))
                    if pattern.name is not None:
                        lookups.appendlist(pattern.name, (bits, p_pattern, pattern.default_args))
            self._reverse_dict[language_code] = lookups
            self._namespace_dict[language_code] = namespaces
            self._app_dict[language_code] = apps
            self._populated = True
            self._local.populating = False

        @property
        def reverse_dict(self):
            language_code = get_language()
            if language_code not in self._reverse_dict:
                self._populate()
            return self._reverse_dict[language_code]

        @property
        def namespace_dict(self):
            language_code = get_language()
            if language_code not in self._namespace_dict:
                self._populate()
            return self._namespace_dict[language_code]

        @property
        def app_dict(self):
            language_code = get_language()
            if language_code not in self._app_dict:
                self._populate()
            return self._app_dict[language_code]

        def _is_callback(self, name):
            if not self._populated:
                self._populate()
            return name in self._callback_strs

        def resolve(self, path):
            path = force_text(path)  # path may be a reverse_lazy object
            tried = []
            match = self.regex.search(path)
            if match:
                new_path = path[match.end():]
                for pattern in self.url_patterns:
                    try:
                        sub_match = pattern.resolve(new_path)
                    except Resolver404 as e:
                        sub_tried = e.args[0].get('tried')
                        if sub_tried is not None:
                            tried.extend([pattern] + t for t in sub_tried)
                        else:
                            tried.append([pattern])
                    else:
                        if sub_match:
                            # Merge captured arguments in match with submatch
                            sub_match_dict = dict(match.groupdict(), **self.default_kwargs)
                            sub_match_dict.update(sub_match.kwargs)

                            # If there are *any* named groups, ignore all non-named groups.
                            # Otherwise, pass all non-named arguments as positional arguments.
                            sub_match_args = sub_match.args
                            if not sub_match_dict:
                                sub_match_args = match.groups() + sub_match.args

                            return ResolverMatch(
                                sub_match.func,
                                sub_match_args,
                                sub_match_dict,
                                sub_match.url_name,
                                [self.app_name] + sub_match.app_names,
                                [self.namespace] + sub_match.namespaces,
                            )
                        tried.append([pattern])
                raise Resolver404({'tried': tried, 'path': new_path})
            raise Resolver404({'path': path})

        @cached_property
        def urlconf_module(self):
            if isinstance(self.urlconf_name, str):
                return import_module(self.urlconf_name)
            else:
                return self.urlconf_name

        @cached_property
        def url_patterns(self):
            # urlconf_module might be a valid set of patterns, so we default to it
            patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
            try:
                iter(patterns)
            except TypeError:
                msg = (
                    "The included URLconf '{name}' does not appear to have any "
                    "patterns in it. If you see valid patterns in the file then "
                    "the issue is probably caused by a circular import."
                )
                raise ImproperlyConfigured(msg.format(name=self.urlconf_name))
            return patterns

        def resolve_error_handler(self, view_type):
            callback = getattr(self.urlconf_module, 'handler%s' % view_type, None)
            if not callback:
                # No handler specified in file; use lazy import, since
                # django.conf.urls imports this file.
                from django.conf import urls
                callback = getattr(urls, 'handler%s' % view_type)
            return get_callable(callback), {}

        def reverse(self, lookup_view, *args, **kwargs):
            return self._reverse_with_prefix(lookup_view, '', *args, **kwargs)

        def _reverse_with_prefix(self, lookup_view, _prefix, *args, **kwargs):
            if args and kwargs:
                raise ValueError("Don't mix *args and **kwargs in call to reverse()!")
            text_args = [force_text(v) for v in args]
            text_kwargs = {k: force_text(v) for (k, v) in kwargs.items()}

            if not self._populated:
                self._populate()

            possibilities = self.reverse_dict.getlist(lookup_view)

            for possibility, pattern, defaults in possibilities:
                for result, params in possibility:
                    if args:
                        if len(args) != len(params):
                            continue
                        candidate_subs = dict(zip(params, text_args))
                    else:
                        if (set(kwargs.keys()) | set(defaults.keys()) != set(params) |
                                set(defaults.keys())):
                            continue
                        matches = True
                        for k, v in defaults.items():
                            if kwargs.get(k, v) != v:
                                matches = False
                                break
                        if not matches:
                            continue
                        candidate_subs = text_kwargs
                    # WSGI provides decoded URLs, without %xx escapes, and the URL
                    # resolver operates on such URLs. First substitute arguments
                    # without quoting to build a decoded URL and look for a match.
                    # Then, if we have a match, redo the substitution with quoted
                    # arguments in order to return a properly encoded URL.
                    candidate_pat = _prefix.replace('%', '%%') + result
                    if re.search('^%s%s' % (re.escape(_prefix), pattern), candidate_pat % candidate_subs):
                        # safe characters from `pchar` definition of RFC 3986
                        url = quote(candidate_pat % candidate_subs, safe=RFC3986_SUBDELIMS + '/~:@')
                        # Don't allow construction of scheme relative urls.
                        if url.startswith('//'):
                            url = '/%%2F%s' % url[2:]
                        return url
            # lookup_view can be URL name or callable, but callables are not
            # friendly in error messages.
            m = getattr(lookup_view, '__module__', None)
            n = getattr(lookup_view, '__name__', None)
            if m is not None and n is not None:
                lookup_view_s = "%s.%s" % (m, n)
            else:
                lookup_view_s = lookup_view

            patterns = [pattern for (possibility, pattern, defaults) in possibilities]
            if patterns:
                if args:
                    arg_msg = "arguments '%s'" % (args,)
                elif kwargs:
                    arg_msg = "keyword arguments '%s'" % (kwargs,)
                else:
                    arg_msg = "no arguments"
                msg = (
                    "Reverse for '%s' with %s not found. %d pattern(s) tried: %s" %
                    (lookup_view_s, arg_msg, len(patterns), patterns)
                )
            else:
                msg = (
                    "Reverse for '%(view)s' not found. '%(view)s' is not "
                    "a valid view function or pattern name." % {'view': lookup_view_s}
                )
            raise NoReverseMatch(msg)

    class LocaleRegexURLResolver(RegexURLResolver):
        """
        A URL resolver that always matches the active language code as URL prefix.

        Rather than taking a regex argument, we just override the ``regex``
        function to always return the active language-code as regex.
        """
        def __init__(
            self, urlconf_name, default_kwargs=None, app_name=None, namespace=None,
            prefix_default_language=True,
        ):
            super().__init__(None, urlconf_name, default_kwargs, app_name, namespace)
            self.prefix_default_language = prefix_default_language

        @property
        def regex(self):
            language_code = get_language() or settings.LANGUAGE_CODE
            if language_code not in self._regex_dict:
                if language_code == settings.LANGUAGE_CODE and not self.prefix_default_language:
                    regex_string = ''
                else:
                    regex_string = '^%s/' % language_code
                self._regex_dict[language_code] = re.compile(regex_string)
            return self._regex_dict[language_code]